Electronic devices utilizing spin torque transfer to flip magnetic orientation

ABSTRACT

Electronic devices that include (i) a magnetization controlling structure; (ii) a tunnel barrier structure; and (iii) a magnetization controllable structure including: a first polarizing layer; and a first stabilizing layer, wherein the tunnel barrier structure is between the magnetization controlling structure and the magnetization controlling structure and the first polarizing layer is between the first stabilizing layer and the tunnel barrier structure, wherein the electronic device has two stable overall magnetic configurations, and wherein a first unipolar current applied to the electronic device will cause the orientation of the magnetization controlling structure to reverse its orientation and a second unipolar current applied to the electronic device will cause the magnetization controllable structure to switch its magnetization in order to obtain one of the two stable overall magnetic configurations, wherein the second unipolar current has an amplitude that is less than the first unipolar current.

PRIORITY

This application claims priority to U.S. application Ser. No. 12/415,243filed Mar. 31, 2009 which claims priority to U.S. ProvisionalApplication No. 61/103,765, entitled “SPIN MOMENTUM TRANSFER (SMT)DRIVEN MAGNETIC FLIP FLOP DEVICE” filed on Oct. 8, 2008, the disclosureof which is incorporated herein by reference.

BACKGROUND

Spintronics is an area of technology that utilizes the spin of electronsto manipulate various properties of a device, such as magnetic state orresistance for example. Much of the technology is based on the phenomenacalled spin momentum transfer effect or spin torque transfer effect.Spin torque transfer effect refers to the effect of a spin-polarizedcurrent when it interacts with the local magnetization of a magneticlayer. There is significant interest in using the spin torque transfereffect as a basis for spin torque driven non-volatile magnetic randomaccess memory (MRAM), magnetic race track memory, MRAM with movingdomain walls, and as interconnects that use spin waves instead ofelectric currents for data propagation. Because of the interest inspintronics for such diverse applications, there is a need for simplebuilding blocks that can be used to create more complex systems.

BRIEF SUMMARY

Disclosed are electronic devices that include (i) a magnetizationcontrolling structure; (ii) a tunnel barrier structure; and (iii) amagnetization controllable structure including: a first polarizinglayer; and a first stabilizing layer, wherein the tunnel barrierstructure is between the magnetization controlling structure and themagnetization controllable structure and the first polarizing layer isbetween the first stabilizing layer and the tunnel barrier structure,wherein the electronic device has two stable overall magneticconfigurations, and wherein a first unipolar current applied to theelectronic device will cause the orientation of the magnetizationcontrolling structure to reverse its orientation and a second unipolarcurrent applied to the electronic device will cause the magnetizationcontrollable structure to switch its magnetization in order to obtainone of the two stable overall magnetic configurations, wherein thesecond unipolar current has an amplitude that is less than the firstunipolar current.

Disclosed are electronic devices that include (i) a magnetizationcontrolling structure having a first magnetic coercivity at a firsttemperature and a second magnetic coercivity at a second temperaturehigher than the first temperature; (ii) a tunnel barrier structure; and(iii) a magnetization controllable structure including a firstpolarizing layer; and a first stabilizing layer, wherein the tunnelbarrier structure is between the magnetization controlling structure andthe magnetization controllable structure and the first polarizing layeris between the first stabilizing layer and the tunnel barrier structure,wherein the first magnetic coercivity of the magnetization controllingstructure is higher than the first magnetic coercivity of themagnetization controllable structure and the second magnetic coercivityof the magnetization controlling structure is lower than the secondmagnetic coercivity of the magnetization controllable structure.

Disclosed are methods of affecting the properties of an electronicdevice that include the steps of providing an electronic device, theelectronic device that includes (i) a magnetization controllingstructure; (ii) a tunnel barrier structure; and (iii) a magnetizationcontrollable structure including a first polarizing layer; and a firststabilizing layer, wherein the tunnel barrier structure is between themagnetization controlling structure and the magnetization controllablestructure and the first polarizing layer is between the firststabilizing layer and the tunnel barrier structure; applying a firstunipolar current to the electronic device, wherein the first currentcauses the magnetization orientation of the magnetization controllingstructure to be flipped; and applying a second unipolar current in thesame direction as the first unipolar current to the electronic device,wherein application of the second unipolar current causes themagnetization orientation of the magnetization controllable structure tobe flipped.

These and various other features and advantages will be apparent from areading of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a schematic representation of an exemplary disclosed device;

FIG. 2 is a schematic representation of an exemplary controllablestructure of a disclosed device;

FIG. 3A is a schematic representation of a disclosed device with bothcontrolling structures and controllable structures that includepolarizing and stabilizing layers respectively;

FIGS. 3B and 3C demonstrate the two stable magnetic configurations ofthe exemplary perpendicular to the plane anisotropy and magnetizationdevice depicted in FIG. 3A;

FIG. 4A depicts the exemplary device of FIG. 3A before a first currentis applied thereto;

FIGS. 4B and 4C depict the exemplary device of FIG. 3A while the firstcurrent is flowing through the device;

FIG. 4D depicts the exemplary device of FIG. 3A while a second currentis applied thereto;

FIGS. 5A, 5B, 5C and 5D illustrate coercivity versus temperatureprofiles of materials that can be utilized for stabilizing layers indisclosed devices;

FIGS. 6A and 6B demonstrate the two stable magnetic configurations of anexemplary in-plane anisotropy and magnetization device;

FIG. 7A depicts the exemplary device of FIG. 6A before a first currentis applied thereto;

FIGS. 7B and 7C depict the exemplary device of FIG. 6A while the firstcurrent is flowing through the device;

FIG. 7D depicts the exemplary device of FIG. 6A while a second currentis applied thereto;

FIG. 8A is a schematic representation of a disclosed device thatincludes a controlling structure having a ferromagnetic layer and anantiferromagnetic layer;

FIG. 8B depicts the exemplary device of FIG. 8A before a first currentis applied thereto;

FIGS. 8C and 8D depict the exemplary device of FIG. 8A while the firstcurrent is flowing through the device;

FIG. 8E depicts the exemplary device of FIG. 8A while a second currentis applied thereto;

FIG. 9 is a schematic representation of a disclosed device with anoptional seed layer and cap layer; and

FIG. 10 depicts an exemplary disclosed method.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

Embodiments other than those specifically discussed herein arecontemplated and may be made without departing from the scope or spiritof the present disclosure. The following detailed description is notlimiting. The definitions provided are to facilitate understanding ofcertain terms frequently used and do not limit the disclosure.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification, use of a singular form of a term, can encompassembodiments including more than one of such term, unless the contentclearly dictates otherwise. For example, the phrase “adding a solvent”encompasses adding one solvent, or more than one solvent, unless thecontent clearly dictates otherwise. As used in this specification andthe appended claims, the term “or” is generally employed in its senseincluding “either or both” unless the context clearly dictatesotherwise.

“Include,” “including,” or like terms means encompassing but not limitedto, that is, including and not exclusive.

Disclosed are electronic devices that utilize the spin torque transfereffect to switch between two magnetic states. The device advantageouslyutilizes unipolar current to affect the switch.

FIG. 1 illustrates an embodiment of a disclosed electronic device 100.An exemplary electronic device 100 includes a magnetization controllingstructure 130 (also referred to simply as a controlling structure 130),a tunnel barrier structure 120, and a magnetization controllablestructure 110 (also referred to simply as a controllable structure 110).A structure, as that term is used herein can, but need not include morethan one layer. In embodiments, a structure (e.g. a controllingstructure 130, a tunnel barrier structure 120 or a controllablestructure 110) can include a single layer of a single material, multiplelayers of a single material or multiple layers of multiple materials.Controllable structure 110 and controlling structure 130 or devices thatinclude such structures can also be referred to as first and secondflip-flop structures or layers.

The controlling structure 130 has a first surface 131 and a secondsurface 132. The tunnel barrier structure 120 has a first surface 121and a second surface 122. The controllable structure 110 has a firstsurface 111 and a second surface 112. In embodiments, the second surface132 of the controlling structure 130 can be adjacent to, directlyadjacent to, or in contact with the first surface 121 of the tunnelbarrier structure 120 (similarly, the first surface 121 of the tunnelbarrier structure 120 can be adjacent to, directly adjacent to, or incontact with the second surface 132 of the controlling structure 130).In embodiments, the second surface 122 of the tunnel barrier structure120 can be adjacent to, directly adjacent to, or in contact with thefirst surface 111 of the controllable structure 110 (similarly, thefirst surface 111 of the controllable structure 110 can be adjacent to,directly adjacent to, or in contact with the second surface 122 of thetunnel barrier structure 120). In embodiments, the tunnel barrierstructure 120 can be located between the controlling structure 130 andthe controllable structure 110. In embodiments, the tunnel barrierstructure 120 can be positioned between the controlling structure 130and the controllable structure 110.

The tunnel barrier structure 120 can generally include a material ormaterials that can afford a relatively large spin momentum transferthrough the structure and are non-magnetic. Exemplary materials includeoxide materials such as alumina (Al₂O₃), titanium oxides (TiO_(x)),magnesium oxide (MgO), zinc oxide (ZnO), hafnium oxide (HfO), galliumoxide (GaO), and combinations thereof. Other useful materials can alsobe utilized for the tunnel barrier structure 120. Any useful thicknessof the material or materials of the tunnel barrier structure 120 can beutilized. In embodiments, the tunnel barrier structure 120 can have athickness from about 0.5 nanometers (nm) to about 15 nm depending atleast in part on the identity of the material or materials making up thetunnel barrier structure 120.

An embodiment of an exemplary controllable structure is depicted in FIG.2. An exemplary controllable structure 210 includes a polarizing layer240 (also referred to as a first polarizing layer 240) and a stabilizinglayer 250 (also referred to as a first stabilizing layer 250. Inembodiments, a “layer” can refer to a single layer of a single material,and in other embodiments, a “layer” can refer to multiple layers of asingle material and in embodiments a “layer” can refer to multiplelayers of multiple materials. The polarizing layer 240 has a firstsurface 241 and a second surface 242. The stabilizing layer 250 has afirst surface 251 and a second surface 252. In embodiments, the secondsurface 242 of the polarizing layer 240 can be adjacent to, directlyadjacent to, or in contact with the first surface 251 of the stabilizinglayer 250, and similarly, the first surface 251 of the stabilizing layer250 can be adjacent to, directly adjacent to, or in contact with thesecond surface 242 of the polarizing layer 240. In embodiments, thefirst surface 211 of the controllable structure 210 can be substantiallycomposed of the polarizing layer 240. In embodiments, the second surface212 of the controllable structure 210 can be substantially composed ofthe stabilizing layer 250. Therefore, in such embodiments, the secondsurface of the tunnel barrier structure (122 in FIG. 1) can be adjacentto, directly adjacent to, or in contact with the first surface 241 ofthe polarizing layer 240 of the controllable structure 210. Inembodiments, the polarizing layer 240 can be between the stabilizinglayer 250 and the tunnel barrier structure (120 in FIG. 1).

Embodiments of disclosed electrical devices include controllingstructures that also include polarizing and stabilizing layers. Anexample of such a device 300 can be seen in FIG. 3A. The device depictedin FIG. 3A includes a controlling structure 330, a tunnel barrierstructure 320 and a controllable structure 310. The controllablestructure 310 includes the polarizing layer 340 (also referred to as asecond polarizing layer 340) and the stabilizing layer 350 (alsoreferred to as a second stabilizing layer 350) as discussed above. Thecontrolling structure 330 in such an exemplary device can include apolarizing layer 360 and a stabilizing layer 370. As in the controllablestructure 310, the polarizing layer 360 has a first surface 361 and asecond surface 362; and the stabilizing layer 370 has a first surface371 and a second surface 372. The second surface 362 of the polarizinglayer 360 of the controlling structure 330 can be adjacent to, directlyadjacent to, or in contact with the first surface (121 in FIG. 1) of thetunnel barrier structure 320 (or similarly, the first surface of thetunnel barrier structure 320 can be adjacent to, directly adjacent to,or in contact with the second surface 362 of the polarizing layer 360 ofthe controlling structure 330). The second surface 372 of thestabilizing layer 370 of the controlling structure 330 can be adjacentto, directly adjacent to, or in contact with the first surface 361 ofthe polarizing layer 360 of the controlling structure 330 (or similarly,the first surface 361 of the polarizing layer 360 of the controllingstructure 330 can be adjacent to, directly adjacent to, or in contactwith the second surface 372 of the stabilizing layer 370 of thecontrolling structure 330). In embodiments, the polarizing layer 340 canbe between the stabilizing layer 350 and the tunnel barrier structure320.

The magnetic materials that are included in disclosed electrical devicescan either have perpendicular to the plane anisotropy and magnetizationor in-plane anisotropy and magnetization. In embodiments, some materialscan be made to have either perpendicular to the plane or in-planeanisotropy by choosing an appropriate seed layer. For example CoPt canhave perpendicular anisotropy if grown on Ru or CrRu but can havein-plane anisotropy if grown on Ti or Ta. As another illustrativeexample, FePt can have perpendicular anisotropy if grown on Pt but canhave in-plane anisotropy if grown on Ru. In embodiments, the anisotropyof some materials cannot be controlled by the choice of seed layers. Forexample, materials such as amorphous TbFeCo or GdTbCoFe usually haveperpendicular anisotropy and materials such as CoFe, CoNiFe, CoFeB havein-plane anisotropy regardless of the seed layer chosen. Devices thathave only magnetic material that is perpendicular to the planeanisotropy and magnetization can be referred to as “perpendicular to theplane anisotropy and magnetization devices” or “perpendicular anisotropydevices”. Devices that have only magnetic material that is in-planeanisotropy and magnetization can be referred to as “in-plane anisotropyand magnetization devices” or “in-plane anisotropy devices”. Materialsthat have perpendicular to the plane anisotropy and magnetization havemagnetic orientations that are perpendicular to a defined plane of thedevice. Materials that have in-plane anisotropy and magnetization havemagnetic orientations that are parallel to a defined plane of thedevice. FIGS. 3B, 3C, 4A, 4B, 4C and 4D depict devices that haveperpendicular to the plane anisotropy and magnetization; and FIGS. 6A,6B, 7A, 7B, 7C and 7D depict devices that have in-plane anisotropy andmagnetization.

A device that has perpendicular to the plane anisotropy andmagnetization will include magnetic materials that only haveperpendicular to the plane anisotropy and magnetization. A device thathas in-plane anisotropy and magnetization will include magneticmaterials that only have in-plane anisotropy and magnetization. Itshould be noted that both perpendicular to the plane anisotropy andmagnetization devices and an in-plane anisotropy and magnetizationdevices will also include non-magnetic materials (e.g. tunnel barrierstructure and optional seed and cap layers).

FIGS. 3B and 3C depict the two stable states of an exemplaryperpendicular to the plane anisotropy and magnetization device. Thedevices depicted in these figures include controlling structures 330,tunnel barrier structures 320 and controllable structures 310 asdiscussed above. The plane of the devices is depicted by the arrowsabove the devices. There are two different magnetic configurations, oneof which the device will automatically revert to after a perturbation.The first is shown in FIG. 3B and has all of the magnetic moments of thecontrolling structure 330 and the controllable structure 310 aligned“up”, referred to as the “stable up configuration”. This is depicted bythe arrows depicting the magnetic moment of the stabilizing layerM_(370a) and the polarizing layer M_(360a) of the controlling structure330; and the magnetic moment of the polarizing layer M_(340a) and thestabilizing layer M_(350a) of the controllable structure 310. The secondstable configuration is shown in FIG. 3C and has all of the magneticmoments of the controlling structure 330 and the controllable structure310 aligned “down”, referred to as the “stable down configuration”. Thisis depicted by the arrows depicting the magnetic moment of thestabilizing layer M_(370b) and the polarizing layer M_(360b) of thecontrolling structure 330; and the magnetic moment of the polarizinglayer M_(340b) and the stabilizing layer M_(350b) of the controllablestructure 310.

FIGS. 4A, 4B, 4C and 4D illustrate the application of unipolar currentto a perpendicular to the plane anisotropy and magnetization device suchas that depicted in FIG. 3A. As seen in FIG. 4A, the device includes acontrolling structure 430 that includes a stabilizing layer 470 and apolarizing layer 460, a tunnel barrier structure 420 (exaggerated foreasier visualization) and a controllable structure 410 that includes apolarizing layer 440 and a stabilizing layer 450. For the sake ofexample, the device is depicted as being in the stable up configuration,although the same principles apply to the stable down configuration.

FIG. 4B shows the device at the instant a first unipolar current isdirected from the controllable structure 410 to the controllingstructure 430 as depicted by the arrow labeled “I” on the left side ofthe figure. Applying current from the controllable structure 410 to thecontrolling structure 430 causes electrons to flow from the controllingstructure 430 to the controllable structure 410, as depicted by thearrow labeled “e⁻” on the left side of the figure. As with allelectrical current, some of the electrons will emerge from thepolarizing layer 460 with their spin up and some will emerge with theirspin down. As seen in this example, a majority of the electrons havetheir spin up. These majority and minority spins are depicted as spin upand spin down respectively in FIG. 4B. The spin up electrons aredepicted on the left of the tunnel barrier structure 420 and the spindown electrons are depicted on the right of the tunnel barrier structure420. As the electrons flow from the controlling structure 430 throughthe tunnel barrier structure 420, the electrons that have a spin that isaligned with the polarizing layer 440 of the controllable structure 410are transmitted through the polarizing layer 440 and through theremainder of the device. The electrons that have a spin that is oppositeto the polarizing layer 440 of the controllable structure 410 are backscattered from the polarizing layer 440 of the controllable structure410. These back scattered electrons create a torque that flips themagnetization orientation of the layers (polarizing layer 460 andstabilizing layer 470) of the controlling structure 430, as seen bycomparing the magnetization vectors M_(460a) and M_(470a) in FIG. 4B tothe magnetization vectors M_(460b) and M_(470b) as seen in FIG. 4C. FIG.4C depicts the device after the magnetization of the controllingstructure 430 has flipped but the current has not yet been altered.

FIG. 4D depicts the device once a second unipolar current is applied tothe device. In this embodiment, the second current that is applied hasan amplitude of zero, stated another way, the unipolar current is shutoff. When the unipolar current is applied, the temperature of the deviceis elevated when compared with the unipolar current being off. Inembodiments, the temperature of the device can be elevated significantlywhen the current is on as compared to when the current is off (ordecreased). In embodiments, the temperature can be elevated by about100° C. when the current is on, when compared to the current being off.As discussed above with respect to FIGS. 3B and 3C, there are two stablemagnetic configurations of such a device, the stable up configurationand the stable down configuration. The device in FIG. 4C, once thecurrent is shut off, is not in a stable configuration; therefore thedevice will affect a change in order to return to one of the stableconfigurations. The materials making up the various structures of thedevice are chosen so that the controllable structure 410 flips itsmagnetic orientation instead of the controlling structure 430 flippingback. As seen in FIG. 4D, the magnetization of the polarizing layer 440and stabilizing layer 450 change from M_(440a) and M_(450a) to M_(440b)and M_(450b) respectively in order for the whole device to be in thestable down configuration, as shown in FIG. 4D.

The polarizing layers in the controlling structure 430 and thecontrollable structure 410 can be, but need not be, the same material.The materials of the polarizing layer are generally not the portion ofthe controlling structure 430 and the controllable structure 410 thataffect the desired magnetization orientation flip. The polarizing layersare generally made of a material that will polarize electrons that flowthrough the material. The materials of the polarizing layers aregenerally chosen to create desirable spin polarization and spin torquetransfer effects. In embodiments, the materials of the polarizing layersare chosen to enhance the spin polarization and spin torque transfereffects. Exemplary materials that can be utilized for polarizing layersinclude cobalt (Co), iron (Fe), cobalt iron alloys (CoFe), cobalt ironboron alloys (CoFeB) and combinations thereof for example. Inembodiments, half metallic materials such as CrO₂, Fe₃O₄, CuMnAl andCuMnSi, for example, may also have advantageous properties.

In embodiments where both the controlling structure 430 and thecontrollable structure 410 include polarizing layers and stabilizinglayers, the materials of the stabilizing layers are chosen so that themagnetization of the controllable structure 410 is effected to conformto the magnetization of the controlling structure 430 and not the otherway around. Generally, the material(s) of the stabilizing layer of thecontrolling structure and the material(s) of the stabilizing layer ofthe controllable structure are chosen to ensure that when the unipolarcurrent is turned off (or decreased), the controllable structureswitches its magnetization in order to become parallel to themagnetization of the controlling structure; instead of the controllingstructure switching its magnetization in order to become parallel to themagnetization of the controllable structure, which would simply causethe device to revert to its original, pre-applied unipolar currentstate.

The coercivity (H_(c)) of a material is the intensity of the appliedmagnetic field required to modify the magnetization of the material. Thelarger the coercivity of a material, the more difficult it is to changethe magnetization of the material. The smaller the coercivity of amaterial, the easier it is to change the magnetization of the material.The coercivity of a material can be different at different temperatures.In general, the coercivity of the controlling structure can be lowerthan the coercivity of the controllable structure at operatingtemperatures of the device (current on) and the coercivity of thecontrollable structure is higher than the coercivity of the controllingstructure at room temperature (current off or decreased).

In embodiments, materials that make up the stabilizing layer of thecontrolling structure and materials that make up the stabilizing layerof the controllable structure can have different coercivities atdifferent temperatures. The coercivity at different temperatures can beimportant because, as discussed above, there can be a difference (inembodiments a significant difference) in the temperature of the devicewhen the unipolar current is on versus off or decreased. Generally, thematerials of the two stabilizing layers can be chosen so that thecoercivity of the stabilizing layer of the controlling structure issmaller than the coercivity of the stabilizing layer of the controllablestructure when the current is on (operating temperature, or a highertemperature) but becomes larger when the current is off or decreased(room temperature or a lower temperature). This ensures that it is thestabilizing layer of the controlling structure that switches when thecurrent is on, but after the current is shut off or decreased, thestabilizing layer of the controlling structure is more stable and forcesthe stabilizing layer of the controllable structure to switch magneticorientation. The graphs in FIGS. 5A, 5B, 5C and 5D depict properties ofpairs of materials that can be utilized in the two stabilizing layers toaffect this phenomenon.

FIG. 5A depicts the coercivity of materials that can be used as thestabilizing layer of the controlling structure 530 and materials thatcan be used as the stabilizing layer of the controllable structure 510.As seen in this partial depiction of a graph of coercivity versustemperature, a material that can be used for the stabilizing layer ofthe controlling structure can have a first coercivity 531 at roomtemperature and a second coercivity 532 at the operating temperature ofthe device. Similarly, a material that can be used for the stabilizinglayer of the controllable structure can have a first coercivity 511 atroom temperature and a second coercivity 512 at the operatingtemperature of the device. Pairs of materials will affect themagnetization effects discussed herein when the first coercivity 531 ofthe controlling structure is higher than the first coercivity 511 of thecontrollable structure (i.e. the coercivity of the stabilizing layer ofthe controlling structure is higher at room temperature than thecoercivity of the stabilizing layer of the controllable structure) andthe second coercivity 532 of the controlling structure is lower than thesecond coercivity 512 of the controllable structure (i.e. the coercivityof the stabilizing layer of the controlling structure is lower atoperating temperature than the coercivity of the stabilizing layer ofthe controlling structure). Materials that have this type of temperaturedependent coercivity properties will ensure that the stabilizing layerof the controlling structure 530 will be easier to switch when thecurrent is on (operating temperature point of the graph) because thecoercivity is lower than the materials of the stabilizing layer of thecontrollable structure 510; and the stabilizing layer of thecontrollable structure 510 will be easier to switch when the current isoff or decreased (room temperature point of the graph) because thecoercivity is lower than the materials of the stabilizing layer of thecontrolling structure 530.

FIG. 5B depicts a larger portion of a coercivity versus temperatureprofile of types of materials that have the general propertiesexemplified by FIG. 5A. The trace labeled 530 a depicts the coercivityof the stabilizing layer of the controlling structure 530 and the tracelabeled 510 a depicts the coercivity of the stabilizing layer of thecontrollable structure 510. Any pair of materials that exhibit acoercivity versus temperature profile similar to that depicted in FIG.5B can be utilized in disclosed devices. In embodiments, ferromagneticmaterials that can be obtained by alloying rare earth metals withtransition metals can be utilized. By changing the composition of thealloy, the high coercivity can be adjusted such that the stabilizinglayer of the controlling structure is large at room temperature whilethe coercivity of the stabilizing layer of the controllable structure islarge at elevated temperatures (such as operating temperatures of thedevice). Rare earth metals include lanthanum (La), cerium (Ce),praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), thulium (Tm) and ytterbium (Yb). Transition metalsinclude scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr),manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc(Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo),technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver(Ag), cadmium (Cd), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten(W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au),mercury (Hg) and lawrencium (Lr). In embodiments, pairs of materialsthat can include for example, alloys of gadolinium (Gd), alloys ofterbium (Tb), alloys of dysprosium (Dy), alloys of cobalt (Co) andalloys of samarium (Sm) can be utilized for example. In embodiments,pairs of materials that can include for example, alloys of gadolinium(Gd) and iron (Fe), alloys of terbium (Tb) and iron (Fe), alloys ofdysprosium (Dy) and iron (Fe) can be utilized for example. Inembodiments, pairs of materials can be chosen from GdFe alloys, TbFealloys and DyFe alloys for example. Specific exemplary pairs ofmaterials include Gd₂₃Fe₇₇ and Gd₂₄Fe₇₆; Tb₁₉Fe₈₁ and Tb₂₁Fe₇₉; andDy₁₇Fe₈₃ and Dy₂₁Fe₇₉.

FIG. 5C depicts another coercivity versus temperature profile of typesof materials that have the general properties exemplified by FIG. 5A.The trace labeled 530 b depicts the coercivity of the stabilizing layerof the controlling structure 530 and the trace labeled 510 b depicts thecoercivity of the stabilizing layer of the controllable structure 510.Any pair of materials that exhibit a coercivity versus temperatureprofile similar to that depicted in FIG. 5C can be utilized. Inembodiments, the stabilizing layer of the controlling structure 530 ismade of a material whose perpendicular anisotropy has a relatively fastmonotonic decrease such as that depicted in trace 530 b. An exemplarypair of materials for the stabilizing layer of the controllablestructure 510 and the controlling structure 530 include a GdTbCoFematerial and a TbCoFe material respectively.

FIG. 5D shows another possible coercivity versus temperature profile oftypes of materials that can be utilized. In such an embodiment thecoercivity 530 c of the stabilizing layer of the controlling structureis higher than the coercivity 510 c of the stabilizing layer of thecontrollable structure at room temperature and also decreases faster astemperature increases. Therefore, at operating temperature, thecoercivity 510 c of the stabilizing layer of the controlling structurewill be higher than the coercivity 530 c of the stabilizing layer of thecontrollable structure. In embodiments that exhibit this type ofbehavior, the stabilizing layer of the controlling structure can be madeof terbium cobalt iron (TbCoFe) alloys and the stabilizing layer of thecontrollable structure can be made of materials including cobaltchromium platinum alloys (CoCrPt), cobalt platinum alloys (CoPt), cobaltplatinum multilayers (Co/Pt), cobalt nickel multilayers (Co/Ni), cobaltcopper multilayers (Co/Cu) and cobalt palladium multilayers (Co/Pd) forexample.

As discussed above, disclosed devices can also have in-plane anisotropyand magnetization. A device that has in-plane anisotropy andmagnetization will include magnetic materials that only have in-planeanisotropy and magnetization. It should be noted however that anin-plane device will also include non-magnetic materials (e.g. tunnelbarrier structure). In-plane devices are affected by stray magneticfields. Stray magnetic fields will dictate the stable configurations ofin-plane devices. Generally, the stable configurations of in-planedevices are anti-parallel.

FIGS. 6A and 6B depict the two stable states of an exemplary in-planedevices. The devices depicted in these figures include controllingstructures 630, tunnel barrier structures 620 and controllablestructures 610 as discussed above. The magnetization plane of thedevices is depicted by the arrows above the devices. There are twodifferent magnetic configurations, one of which the device willautomatically revert to after a perturbation. The first is shown in FIG.6A and has the magnetic moments of the controlling structure 630anti-parallel to the magnetic moments of the controllable structure 610,referred to as “stable right-left configuration”. This is depicted bythe arrows depicting the magnetic moment of the stabilizing layerM_(671c) and the polarizing layer M_(661c) of the controlling structure630 that both have “right” orientations; and the magnetic moment of thepolarizing layer M_(641d) and the stabilizing layer M_(651d) of thecontrollable structure 610 that both have “left” orientations. Thesecond is shown in FIG. 6B and also has the magnetic moments of thecontrolling structure 630 and the controllable structure 610anti-parallel but in the opposite configuration, referred to as “stableleft-right configuration”. This is depicted by the arrows depicting themagnetic moment of the stabilizing layer M_(671d) and the polarizinglayer M_(661d) of the controlling structure 630 that both have “left”orientations; and the magnetic moment of the polarizing layer M_(641c)and the stabilizing layer M_(651c) of the controllable structure 610that both have “right” orientations.

FIGS. 7A, 7B, 7C and 7D illustrate the application of unipolar currentto an in-plane anisotropy and magnetization device. As seen in FIG. 7A,the device includes a controlling structure 730 that includes astabilizing layer 771 and a polarizing layer 761, a tunnel barrierstructure 720 (exaggerated for easier visualization) and a controllablestructure 710 that includes a polarizing layer 741 and a stabilizinglayer 751. For the sake of example, the device is depicted as being inthe “stable right-left configuration”, although the same principlesapply to the “stable left-right configuration”.

FIG. 7B depicts the device once a first unipolar current is applied. Asopposed to the perpendicular to the plane anisotropy and magnetizationdevice, the current in an in-plane anisotropy and magnetization deviceis applied from the controlling structure 730 to the controllablestructure 710. Therefore, unipolar current is directed from thecontrolling structure 730 to the controllable structure 710 as depictedby the arrow labeled “I” on the left side of the figure. This causeselectrons to flow from the controllable structure 710 to the controllingstructure 730, as depicted by the arrow labeled “e⁻” on the left side ofthe figure. The electrons that flow through the polarizing layer 741will have both majority and minority spins. These majority and minorityspins are depicted as spin left and spin right respectively. In thisexample, a majority of the electrons are spin left electrons. The spinleft electrons are shown on the left of the tunnel barrier structure 720and the spin right electrons are shown on the right of the tunnelbarrier structure 720.

As the electrons flow from the controllable structure 710 through thetunnel barrier structure 720, the electrons that have spins that arealigned with the polarizing layer 761 of the controlling structure 730are transmitted through the polarizing layer 761 and through theremainder of the device (as depicted for the electrons on the right ofthe tunnel barrier structure 720). The electrons that have a spin thatis opposite to the polarizing layer 761 of the controlling structure 730(spin left electrons) enter the polarizing layer 761 of the controllingstructure 730 and because they are opposite to the magnetization of thepolarizing layer 761 create a torque that exerts a force on themagnetization of the polarizing layer 761 of the controlling structure730. It should also be noted that some of the left spin majorityelectrons are back scattered from the polarizing layer 761 but becausethey are aligned with the magnetization of the polarizing layer 741 andthe stabilizing layer 751 they do not exert a torque on the polarizinglayer 741 and the stabilizing layer 751 of the controllable structure710. The torque that is exerted on the polarizing layer 761 of thecontrolling structure 730 by the majority spin left electrons functionsto flip the magnetization of the polarizing layer 761 and thestabilizing layer 771 of the controlling structure 730. This can be seenby comparing the magnetization vectors M_(761c) and M_(771c) in FIG. 7Bto the magnetization vectors M_(761d) and M_(771d) seen in FIG. 7C. FIG.7C depicts the device after the magnetization of the controllingstructure 730 has flipped but the current has not yet been altered.

FIG. 7D depicts the device after the unipolar current is shut off ordecreased. As discussed above with respect to FIGS. 6A and 6B, there aretwo stable magnetic configurations, the stable left-right configurationand the stable right-left configuration. The device in FIG. 7C, once nocurrent is running through it is not in a stable configuration becauseall of the magnetic orientations are parallel; therefore the device willaffect a change in order to return to one of the stable configurations.The materials making up the device are chosen so that the polarizinglayer 741 and stabilizing layer 751 of the controllable structure 710flips its magnetic orientation instead of the controlling structure 730flipping its orientation and assumes the configuration shown in FIG. 7D.As seen in FIG. 7D, the magnetization of the polarizing layer 741 andstabilizing layer 751 change from M_(741d) and M_(751d) to M_(741c) andM_(751c) respectively in order for the whole device to be in the stableleft right configuration, as shown in FIG. 7D.

The materials of the polarizing layers and the pairs of stabilizinglayers can be the same in in-plane anisotropy and magnetization devicesas they were in perpendicular to the plane anisotropy and magnetizationdevices with the exception that the magnetization vectors are orienteddifferently (in-plane versus perpendicular to the plane).

Another exemplary embodiment of a disclosed device includes acontrolling structure that does not include a stabilizing layer andpolarizing layer but instead includes a ferromagnetic layer that isexchange coupled to an antiferromagnetic layer. An exemplary embodimentis depicted in FIG. 8A. The device 800 depicted in FIG. 8A includes acontrollable structure 810 and a tunneling barrier structure 820 asdiscussed above. The controlling structure 830 in embodiments such asthese includes an antiferromagnetic layer 880 and a ferromagnetic layer890. The antiferromagnetic layer 880 has a first surface 881 and asecond surface 882. The ferromagnetic layer 890 has a first surface 891and a second surface 892. The second surface 882 of theantiferromagnetic layer 880 can be adjacent to, directly adjacent to orin contact with the first surface 891 of the ferromagnetic layer 890(similarly, the first surface 891 of the ferromagnetic layer 890 can beadjacent to, directly adjacent to or in contact with the second surface882 of the antiferromagnetic layer). The second surface 892 of theferromagnetic layer 890 can be adjacent to, directly adjacent to, or incontact with the first surface of the tunneling barrier structure 820(similarly, the first surface of the tunneling barrier structure 820 canbe adjacent to, directly adjacent to, or in contact with the secondsurface 892 of the ferromagnetic layer 890). The first surface 831 ofthe controlling structure 830 can be substantially composed of theantiferromagnetic layer 880 and the second surface 832 of thecontrolling structure 830 can be substantially composed of theferromagnetic layer 890.

An antiferromagnetic layer generally includes two sublattices ofmagnetic moments pointing in opposite directions. When a ferromagneticlayer is in contact with it, the magnetization of the ferromagneticlayer is pinned to the magnetic orientation of the antiferromagenticlayer. Examples of suitable materials for the antiferomagentic layerinclude PtMn, IrMn, PtPdMn, FeMn, NiMn and others.

The ferromagnetic layer may be made of any useful ferromagnetic materialsuch as, for example, Fe, Co or Ni and alloys thereof, such as NiFe andCoFe, and ternary alloys, such as CoFeB. Either or both of theferromagnetic layer and antiferromagnetic layer may be either a singlelayer or an unbalanced synthetic antiferromagnetic (SAF) coupledstructure, i.e., two ferromagnetic sublayers separated by a metallicspacer, such as Ru or Cu, with the magnetization orientations of thesublayers in opposite directions to provide a net magnetization. Eitheror both of the ferromagnetic layer and antiferromagnetic layer can beabout 0.1 nm to about 10 nm thick, depending on the material.

Devices such as those depicted in FIG. 8A also have two stableconfigurations. The first is shown in FIG. 8B and has the magneticmoments of the controlling structure 830 anti-parallel to the magneticmoments of the controllable structure 810, referred to again as “stableright-left configuration”. This is depicted by the arrows depicting themagnetic moment of the antiferromagnetic layer M_(880c) and theferromagnetic layer M_(890c) of the controlling structure 830 that bothhave right orientations; and the magnetic moment of the polarizing layerM_(841d) and the stabilizing layer M_(851d) of the controllablestructure 810 that both have left orientations. The second stableconfiguration (not depicted) is the opposite and is referred to as the“stable left-right configuration”. In this configuration, the magneticmoment of the antiferromagnetic layer 880 and the ferromagnetic layer890 of the controlling structure 830 would both have left orientations(as opposed to the right orientations shown in FIG. 8B); and themagnetic moment of the polarizing layer 841 and the stabilizing layer851 of the controllable structure 810 would both have right orientations(as opposed to the left orientations shown in FIG. 8B).

FIG. 8C depicts the device of FIG. 8B once a first unipolar current isapplied from the controlling structure 830 to the controllable structure810 (as depicted by the arrow labeled I). In this example, a majority ofthe electrons are spin left electrons. The spin left electrons are shownon the left of the tunnel barrier structure 820 and the spin rightelectrons are shown on the right of the tunnel barrier structure 820. Asthe electrons flow from the controllable structure 810 to thecontrolling structure 830, the electrons that are aligned with theferromagnetic layer 890 are transmitted through the ferromagnetic layer890 and through the remainder of the device. The electrons that have aspin that us opposite to the ferromagnetic layer 890 enter theferromagnetic layer 890 and because they are opposite create a torquethat exerts a force on the ferromagnetic layer 890. It should also benoted that some of these electrons are back scattered but because theyare aligned with the magnetization of the polarizing layer 841 and thestabilizing layer 851 they do not exert a torque on the controllablestructure 810.

Application of a first current will also cause the antiferromagneticlayer 880 to become superparamagentic, i.e., it will have no majoritymagnetic orientation and the magnetic moments of the antiferromagneticlayer 880 will become randomized. This will “unpin” the ferromagneticlayer 890, which allows its magnetic orientation to be switched by thetorque from the electrons that are opposite to the magnetization of theferromagnetic layer 890. Specifically, the opposite spin electrons thatenter the ferromagnetic layer 890 of the controlling structure 830 willexert a spin torque on the ferromagnetic layer 890 and cause itsorientation to be flipped from M_(890c) (as shown in FIG. 8C) toM_(890d) (as shown in FIG. 8D). FIG. 8D depicts the device after theantiferromagnetic layer 880 has become superparamagnetic and themagnetization vector of the ferromagnetic layer 890 has been flipped butbefore the second current has been applied (i.e. a current less than thefirst current or a current of zero amplitude).

FIG. 8E depicts the device once the current is turned off or decreased.The antiferromagnetic layer 880 cools down and becomes exchange coupledto the ferromagnetic layer 890 (in this example the ferromagnetic layer890 has a left orientation M_(890d) because of the influence of the spintorque of the opposite spin electrons that entered the ferromagneticlayer 890) thereby changing its magnetic orientation to a leftorientation as well M_(880d). The magnetic field from the ferromagneticlayer 890 then affects the controllable structure 810 and changes theorientation of the polarizing layer 841 and the stabilizing layer 851 toM_(841c) and M_(851c) respectively. This causes the device to take onthe stable left right configuration shown in FIG. 8E.

For the controllable structure 810 to be flipped by the controllingstructure 830, the exchange field from the antiferromagnetic layer 880must be larger than the coercivity (H_(c)) of the controllable structure810. Such is the case when the ferromagnetic layer 890 is a materialthat is generally a soft magnetic material (i.e. has a low magneticanisotropy) and the antiferromagnetic layer 880 is a material that has arelatively low blocking temperature. In embodiments, a soft magneticmaterial is one with an intrinsic anisotropy of less than about 100Oersted (Oe) for example. In embodiments, a material that has arelatively low blocking temperature is one that has a blockingtemperature of less than about 150° C., for example.

In embodiments such as those depicted in FIG. 8A-8E, it may beadvantageous to maintain some level of current through the device at alltimes, instead of turning the current on an turning the current off. Inembodiments, a first current can be applied and then a second currentcan be applied, with the second current having an amplitude that is lessthan the first current. This may cause the temperature to drop enoughthat the antiferromagnetic layer 880 can reorder magnetically and oncecombined with the spin torque from the controllable structure 810stabilize the ferromagnetic layer 890 during the time necessary forexchange coupling of the antiferromagnetic layer 880 to become largerthan the coercivity of the controllable structure 810.

Disclosed devices can also optionally include additional layers. FIG. 9demonstrates an exemplary embodiment of a device that includes acontrolling structure 930, a tunneling barrier structure 920 and acontrollable structure 910. This exemplary device can also include a caplayer 905. The cap layer 905 can be positioned adjacent to, directlyadjacent to or in contact with the second surface 912 of thecontrollable structure 910. A cap layer 905 can generally function toprotect the device from environmental conditions. Exemplary materialsfor cap layer 905 can include tantalum (Ta) or tantalum nitride (TaN)for example. In embodiments a layer of Ta or TaN of about 100 Angstroms(Å) can be utilized as a cap layer 905. Any of the embodiments depicted,described or disclosed herein can optionally include a cap layer.

Another optional layer that can be included in disclosed devices is aseed layer. The exemplary device depicted in FIG. 9 includes a seedlayer 935. The seed layer 935 can be positioned adjacent to, directlyadjacent to or in contact with the first surface 931 of the controllingstructure 930. A seed layer 935 can generally function to assist theformation and structural stability of the device and specifically thefirst surface 931 of the controlling structure 930. The materials thatmake up the seed layer 935 can vary and can depend at least in part onthe particular components that make up the first portions, i.e. thefirst surface 931 of the controlling structure 930. Any of theembodiments depicted, described or disclosed herein can optionallyinclude a seed layer.

Disclosed devices provide a magnetic device that can be easily switchedusing a unipolar current through the spin torque transfer effect. Theability to switch the device using unipolar current as opposed tobipolar current can provide advantages for numerous applications.Devices disclosed herein can be utilized in forming non-volatilemagnetic random access memory (MRAM); in various electricalapplications, devices disclosed herein can be utilized as switches forexample such as for on-chip power mode control; and in routers such asswitch based routers or field programmable gate arrays (FPGA) forexample.

Methods of affecting the properties of an electronic device are alsodisclosed herein. One such exemplary method is exemplified by FIG. 10.The method 1000 includes the steps of providing a device 1010, applyinga first current to the device 1020 and applying a second current to thedevice 1030. The step of providing a device may be accomplished bymanufacturing a device as disclosed herein or obtaining apre-manufactured device as disclosed herein.

The step 1020 of applying a first current to the device may beaccomplished using generally utilized electrical connections. The firstcurrent that is applied to the device is a unipolar current. Theamplitude and other properties of the first current can depend at leastin part on the materials that make up the device and the application forwhich the device will be utilized. The current can be applied to thedevice in one of two ways, by applying the current in a direction thathas it flowing from the controlling structure to the controllablestructure or by applying the current in a direction that has it flowingfrom the controllable structure to the controlling structure. Theparticular direction of current flow that will be chosen can depend onthe type of device. For example, if the device is a perpendicular to theplane anisotropy and magnetization device current can be applied to flowfrom the controllable structure to the controlling structure of thedevice. If the device is an in-plane anisotropy and magnetization devicecurrent can be applied to flow from the controlling structure to thecontrollable structure of the device.

The step 1020 of applying a first current to the device will cause themagnetization orientation of the magnetization controlling structure tobe flipped. For example, in the case of a perpendicular to the planeanisotropy and magnetization device, applying a current from thecontrollable structure to the controlling structure of the device willcause the magnetization orientation of the magnetization controllingstructure to be flipped from up to down or down to up. In perpendicularto the plane anisotropy and magnetization devices, the flip inmagnetization orientation of the controlling structure is caused by thespin torque exhibited by the minority electron spins. In the case of anin-plane anisotropy and magnetization device, applying a current fromthe controlling structure to the controllable structure of the devicewill cause the magnetization orientation of the magnetizationcontrolling structure to be flipped from right to left or left to right.In in-plane anisotropy and magnetization devices, the flip inmagnetization orientation of the controlling structure is caused by thespin torque exhibited by the majority electron spins.

The next step 1030 is to apply a second current to the device. Thesecond current is applied in the same direction as the first current.The second current generally has an amplitude that is less than thefirst current. In embodiments, applying a second current to the deviceincludes ceasing application of a current, i.e. there is no secondcurrent applied to the device, or the second current has an amplitude of0 V. In embodiments, applying a second current to the device includesapplying a current that has an amplitude that is less than the firstcurrent but is not zero. The step of applying the second current may beaccomplished by turning off the source of current or altering theelectrical connections to effectively turn off the source of current tothe device, or by decreasing the amplitude of the current from thesource of current or by altering the electrical connections toeffectively diminish the amplitude of the current.

The step 1030 of applying a second current will cause the magnetizationorientation of the magnetization controllable structure to be flipped.For example, in the case of a perpendicular to the plane anisotropy andmagnetization device, applying a second current will cause themagnetization orientation of the magnetization controllable structure tobe flipped from up to down or down to up. In the case of an in-planeanisotropy and magnetization device, applying a current from thecontrolling structure to the controllable structure of the device willcause the magnetization orientation of the magnetization controllablestructure to be flipped from right to left or left to right. In bothperpendicular and in-plane anisotropy and magnetization devices, theflip of the magnetization controllable structures is caused by thedemagnetization field (also referred to as stray field) from thecontrolling structure acting on the controllable structure to obtain oneof the magnetically stable configurations of the device. Inperpendicular to the plane anisotropy and magnetization devices, oncethe magnetization orientation of the magnetization controllablestructure is flipped, the magnetization orientation of the magnetizationcontrolling structure and the magnetization orientation of themagnetization controllable structure are parallel. In an in-planeanisotropy and magnetization device, once the magnetization orientationof the magnetization controllable structure is flipped, themagnetization orientation of the magnetization controlling structure andthe magnetization orientation of the magnetization controllablestructure are anti-parallel.

Methods that include other steps not disclosed herein carried outbefore, after or in between the steps disclosed herein are alsocontemplated by the disclosure.

Thus, embodiments of ELECTRONIC DEVICES UTILIZING SPIN TORQUE TRANSFERTO FLIP MAGNETIC ORIENTATION are disclosed. The implementationsdescribed above and other implementations are within the scope of thefollowing claims. One skilled in the art will appreciate that thepresent disclosure can be practiced with embodiments other than thosedisclosed. The disclosed embodiments are presented for purposes ofillustration and not limitation, and the present disclosure is limitedonly by the claims that follow.

1. An electronic device comprising: a magnetization controllingstructure; wherein the magnetization controlling structure has a firstmagnetic coercivity at a first temperature and a second magneticcoercivity at a second temperature higher than the first temperature; atunnel barrier structure; and a magnetization controllable structurecomprising: a first polarizing layer; and a first stabilizing layer,wherein the magnetization controllable structure has a first magneticcoercivity at the first temperature and a second magnetic coercivity atthe second temperature, wherein the tunnel barrier structure is betweenthe magnetization controlling structure and the magnetizationcontrollable structure and the first polarizing layer is between thefirst stabilizing layer and the tunnel barrier structure and wherein thefirst magnetic coercivity of the magnetization controlling structure ishigher than the first magnetic coercivity of the magnetizationcontrollable structure and the second magnetic coercivity of themagnetization controlling structure is lower than the second magneticcoercivity of the magnetization controllable structure.
 2. Theelectronic device according to claim 1, wherein the magnetizationcontrolling structure comprises a second polarizing layer and a secondstabilizing layer.
 3. The electronic device according to claim 2,wherein the first temperature is room temperature and the secondtemperature is the operating temperature of the electronic device, andthe first and second stabilizing layers comprise materials withdifferent magnetic coercivities at different temperatures.
 4. Theelectronic device according to claim 2, wherein the first and secondpolarizing layers are independently chosen from the group consisting of:cobalt (Co), iron (Fe), cobalt iron alloys (CoFe), cobalt iron boronalloys (CoFeB), and combinations thereof.
 5. The electronic deviceaccording to claim 2, wherein the first and second stabilizing layersare independently chosen from the group consisting of: alloys ofgadolinium (Gd), alloys of terbium (Tb), alloys of dysprosium (Dy),alloys of cobalt (Co) and alloys of samarium (Sm).
 6. The electronicdevice according to claim 2, wherein the first and second stabilizinglayers are independently chosen from GgTbCoFe and TbCoFe.
 7. Theelectronic device according to claim 2, wherein the first stabilizinglayer is chosen from the group consisting of: CoCrPt, CoPt, Co/Pt Co/Ni,Co/Cu and Co/Pd; and the second stabilizing layer comprises TbCoFe.
 8. Amethod of affecting the properties of an electronic device comprisingthe steps of: providing an electronic device, the electronic devicecomprising a magnetization controlling structure; wherein themagnetization controlling structure has a first magnetic coercivity at afirst temperature and a second magnetic coercivity at a secondtemperature higher than the first temperature; a tunnel barrierstructure; and a magnetization controllable structure comprising: afirst polarizing layer; and a first stabilizing layer, wherein themagnetization controllable structure has a first magnetic coercivity atthe first temperature and a second magnetic coercivity at the secondtemperature, wherein the tunnel barrier structure is between themagnetization controlling structure and the magnetization controllablestructure and the first polarizing layer is between the firststabilizing layer and the tunnel barrier structure and wherein the firstmagnetic coercivity of the magnetization controlling structure is higherthan the first magnetic coercivity of the magnetization controllablestructure and the second magnetic coercivity of the magnetizationcontrolling structure is lower than the second magnetic coercivity ofthe magnetization controllable structure; applying a first unipolarcurrent to the electronic device, wherein the first current causes themagnetization orientation of the magnetization controlling structure tobe flipped; and applying a second unipolar current in the same directionas the first unipolar current to the electronic device, whereinapplication of the second unipolar current causes the magnetizationorientation of the magnetization controllable structure to be flipped.9. The method according to claim 8, wherein the magnetizationcontrollable structure has magnetic anisotropy that is perpendicular tothe plane of the device.
 10. The method according to claim 9, whereinthe current is passed through the device from the magnetizationcontrollable structure to the magnetization controlling structure. 11.The method according to claim 9, wherein once the magnetizationorientation of the magnetization controllable structure is flipped, themagnetization orientation of the magnetization controlling structure andthe magnetization orientation of the magnetization controllablestructure are parallel.
 12. The method according to claim 8, wherein themagnetization controllable structure has magnetic anisotropy that isparallel to the plane of the device.
 13. The method according to claim12, wherein the current is passed through the device from themagnetization controlling structure to the magnetization controllablestructure.
 14. An electronic device comprising: a magnetizationcontrollable structure comprising: a first polarizing layer; and a firststabilizing layer; a tunnel barrier structure; and a magnetizationcontrolling structure comprising: an antiferromagnetic layer; and aferromagnetic layer exchange coupled to the antiferromagnetic layer,wherein the tunnel barrier structure is between the magnetizationcontrolling structure and the magnetization controllable structure andthe first polarizing layer is between the first stabilizing layer andthe tunnel barrier structure, wherein the electronic device has twostable overall magnetic configurations.
 15. The electronic deviceaccording to claim 14, wherein the first stabilizing layer is chosenfrom the group consisting of: alloys of gadolinium (Gd), alloys ofterbium (Tb), alloys of dysprosium (Dy), alloys of cobalt (Co) andalloys of samarium (Sm).
 16. The electronic device according to claim14, wherein the first stabilizing layer is chosen from the groupconsisting of: GgTbCoFe and TbCoFe.
 17. The electronic device accordingto claim 14, wherein the first stabilizing layer is chosen from thegroup consisting of: CoCrPt, CoPt, Co/Pt Co/Ni, Co/Cu and Co/Pd.
 18. Theelectronic device according to claim 14 further comprising a seed layerand a cap layer.
 19. The electronic device according to claim 14,wherein the magnetization controlling structure comprises a secondpolarizing layer and a second stabilizing layer.
 20. The electronicdevice according to claim 19, wherein the first stabilizing layer ischosen from the group consisting of: CoCrPt, CoPt, Co/Pt Co/Ni, Co/Cuand Co/Pd; and the second stabilizing layer comprises TbCoFe.